Approach Considerations
Lab studies
No blood or urine laboratory tests are diagnostic of polymorphic eruption of pregnancy (PEP) and are not typically performed. One large series of cases showed a significant reduction of serum cortisol levels in patients with PEP compared with normal pregnant controls. [11]
Serum submitted for indirect immunofluorescence or NC16a enzyme-linked immunosorbent assay may help to differentiate between PEP and pemphigoid gestationis when the clinical diagnosis is unclear. [21] Both studies detect autoantibodies that are present in persons with pemphigoid gestationis but are not present in those with PEP.
Direct immunofluorescence
In punch biopsy specimens of the skin, direct immunofluorescence (DIF) characteristically is negative in PEP. DIF results differentiate PEP from pemphigoid gestationis when the clinical diagnosis is unclear. The latter disorder is a rare, autoimmune blistering disease characterized by linear deposits of C3 along the basement membrane zone.
Histologic findings
Skin biopsy is rarely necessary. Routine biopsy specimens from PEP usually reveal a normal epidermis, but focal spongiosis and parakeratosis may be seen. Within the papillary dermis and mid dermis, a lymphohistiocytic infiltrate with a variable number of eosinophils and dermal edema is present. [22]
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Papules within prominent striae distensae. Courtesy of Jeffrey P. Callen, MD of Louisville, Kentucky.
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Papules within prominent striae distensae. Courtesy of Jeffrey P. Callen, MD of Louisville, Kentucky.
